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• Lossless avi encoding on linux

  31 août 2012, par JohnSavage

  I am trying to write video using opencv. It is important for me to do this precisely - so it has to be a lossless codec. I am working with OpenCV 2.4.1 on Ubuntu 12.04

  Previously, I was using the fourcc code 0. This gave me the exact result I wanted, and I was able to recover the images perfectly.

  I am not sure what happened, but as of a recent update (around Jul 20th 2012), something went wrong and I am no longer able to write files with this fourcc code. I really don't remember what it was, but it could have come from doing an update, removing some software from my software center, and some other things I did during general cleaning...

  When I check an older file with mediainfo (http://www.fourcc.org/identifier/) I see the following result :

  Complete name                            : oldsample.avi
  
  Format                                   : AVI
  
  Format/Info                              : Audio Video Interleave
  
  Format profile                           : OpenDML
  
  File size                                : 1.07 GiB
  
  Duration                                 : 41s 467ms
  
  Overall bit rate                         : 221 Mbps
  
  Writing application                      : Lavf53.5.0
  
  Video
  
  ID                                       : 0
  
  Format                                   : RGB
  
  Codec ID                                 : 0x00000000
  
  Codec ID/Info                            : Basic Windows bitmap format. 1, 4 and 8 bpp     versions are palettised. 16, 24 and 32bpp contain raw RGB samples
  
  Duration                                 : 41s 467ms
  
  Bit rate                                 : 221 Mbps
  
  Width                                    : 640 pixels
  
  Height                                   : 4294966 816 pixels
  
  Display aspect ratio                     : 0.000
  
  Frame rate                               : 30.000 fps
  
  Bit depth                                : 8 bits
  
  Stream size                              : 1.07 GiB (100%)

  Now, I see that when I write using the 0 fourcc codec, the program actually defaults to the i420 codec. Here is the output from one of the files I try to write now :

  Complete name                            : newsample.avi
  
  Format                                   : AVI
  
  Format/Info                              : Audio Video Interleave
  
  File size                                : 73.0 MiB
  
  Duration                                 : 5s 533ms
  
  Overall bit rate                         : 111 Mbps
  
  Writing application                      : Lavf54.6.100
  
  Video
  
  ID                                       : 0
  
  Format                                   : YUV
  
  Codec ID                                 : I420
  
  Codec ID/Info                            : 8 bit Y plane followed by 8 bit 2x2 subsampled U and V planes.
  
  Duration                                 : 5s 533ms
  
  Bit rate                                 : 111 Mbps
  
  Width                                    : 640 pixels
  
  Height                                   : 480 pixels
  
  Display aspect ratio                     : 4:3
  
  Frame rate                               : 30.000 fps
  
  Compression mode                         : Lossless
  
  Bits/(Pixel*Frame)                       : 12.000
  
  Stream size                              : 72.9 MiB (100%)

  This format, and other formats I try to use (like huffyuv HFYU), do not work for me because I end up with effects like this http://imgur.com/a/0OC4y - you see the bright artifacts coming in due to what I assume is either lossy compression or chroma subsampling in the case of HFYU which is supposed to be lossless. What you are looking at is the red channel from one of my videos. The perceptual effect is negligible when you look at all 3 channels simultaneously but it is essential that I reconstruct the images exactly.

  Furthermore, while I am able to play my old files in media players like vlc, I suddenly find them to be completely incompatible with opencv. When I try to open the older files with a videocapture, the open step works fine, but trying to do a read operation results in a segfault. Furthermore, When I try to write with either :

  CV_FOURCC(0,0,0,0)
  
  0

  Opencv defaults to I420 for some reason.

  Next, I tried using some alternate codecs. 'DIB ' seems like something that should work for me, and on the opencv website (http://opencv.willowgarage.com/wiki/VideoCodecs) it is listed as a 'recommended' codec. However, trying to use this results in the following message :

  OpenCV-2.4.1/modules/highgui/src/cap_gstreamer.cpp:483: error: (-210) Gstreamer Opencv backend doesn't support this codec acutally. in function CvVideoWriter_GStreamer::open
  
  
  
  Aborted (core dumped)

  I checked the opencv source for this codec, and stumbled across the following :

  cd OpenCV-2.4.1/modules
  
  grep -i -r "CV_FOURCC" ./*
  
  ...
  
  ./highgui/src/cap_qt.cpp:    /*if( fourcc == CV_FOURCC( 'D', 'I', 'B', ' ' ))
  
  ./highgui/include/opencv2/highgui/highgui_c.h:#define CV_FOURCC_DEFAULT CV_FOURCC('I', 'Y', 'U', 'V') /* Use default codec for specified filename (Linux only) */

  I tried installing qt4 and reconfiguring with the WITH_QT flag, but that did not change anything. I also tried uncommenting that part of the code and reinstalling opencv, but that also did not work.

  My ultimate goal is for any way to efficiently store and retrieve a video stream with 16 bits for every pixel (like 32float would work fine, and then it wouldn't need to be perfect). Right now I am unpacking the 16 bits into the red and green channels, which is why I need it to be perfect - since an error of 1 in the red channel is multiplied by 256 in the final result. I am not having success with any of the fourcc codes available to me.

• How to change metadata with ffmpeg/avconv without creating a new file ?

  15 avril 2014, par tampis

  I am writing a python script for producing audio and video podcasts. There are a bunch of recorded media files (audio and video) and text files containing the meta information.

  Now I want to program a function which shall add the information from the meta data text files to all media files (the original and the converted ones). Because I have to handle many different file formats (wav, flac, mp3, mp4, ogg, ogv...) it would be great to have a tool which add meta data to arbitrary formats.

  My Question :

  How can I change the metadata of a file with ffmpeg/avconv without changing the audio or video of it and without creating a new file ? Is there another commandline/python tool which would do the job for me ?

  What I tried so far :

  I thought ffmpeg/avconv could be such a tool, because it can handle nearly all media formats. I hoped, that if I set -i input_file and the output_file to the same file, ffmpeg/avconv will be smart enough to leave the file unchanged. Then I could set -metadata key=value and just the metadata will be changed.

  But I noticed, that if I type avconv -i test.mp3 -metadata title='Test title' test.mp3 the audio test.mp3 will be reconverted in another bitrate.

  So I thought to use -c copy to copy all video and audio information. Unfortunately also this does not work :

  :~$ du -h test.wav # test.wav is 303 MB big
  
  303M    test.wav
  
  
  
  :~$ avconv -i test.wav -c copy -metadata title='Test title' test.wav
  
  avconv version 0.8.3-4:0.8.3-0ubuntu0.12.04.1, Copyright (c) 2000-2012 the
  
  Libav    developers
  
  built on Jun 12 2012 16:37:58 with gcc 4.6.3
  
  [wav @ 0x846b260] max_analyze_duration reached
  
  Input #0, wav, from 'test.wav':
  
  Duration: 00:29:58.74, bitrate: 1411 kb/s
  
      Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
  
  File 'test.wav' already exists. Overwrite ? [y/N] y
  
  Output #0, wav, to 'test.wav':
  
  Metadata:
  
      title           : Test title
  
      encoder         : Lavf53.21.0
  
      Stream #0.0: Audio: pcm_s16le, 44100 Hz, 2 channels, 1411 kb/s
  
  Stream mapping:
  
  Stream #0:0 -> #0:0 (copy)
  
  Press ctrl-c to stop encoding
  
  size=     896kB time=5.20 bitrate=1411.3kbits/s    
  
  video:0kB audio:896kB global headers:0kB muxing overhead 0.005014%
  
  
  
  :~$ du -h test.wav # file size of test.wav changed dramatically
  
  900K    test.wav

  You see, that I cannot use -c copy if input_file and output_file are the same. Of course I could produce a temporarily file :

  :-$ avconv -i test.wav -c copy -metadata title='Test title' test_temp.mp3
  
  :-$ mv test_tmp.mp3 test.mp3

  But this solution would create (temporarily) a new file on the filesystem and is therefore not preferable.

• Shared Hosting + Static FFMPEG + PHP (or other scripting language) == failure on finding codec

  7 juillet 2012, par Ethan Allen

  here is the following environment :

  1. 1and1 shared hosting (they do not have ffmpeg installed, all good)
  2. i built a static ffmpeg binary that does not require dynamic loading of shared libaries (i built this on an Ubuntu system)
  3. ffmpeg binary is fully accessible and is able to get access
  4. executing the same command terminal or executing a php/perl script via terminal works fine...however, both scripts through a browser/web request fails with the following :

      Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
      array
  
        0 => string 'ffmpeg version git-2012-07-06-6936111 Copyright (c) 2000-2012 the FFmpeg developers' (length=83)
  
        1 => string '  built on Jul  5 2012 23:04:34 with gcc 4.4.3' (length=46)
  
        2 => string '  configuration : —prefix=' /ffmpeg' —enable-gpl —enable-libfaac —enable-libmp3lame —enable-libopencore-amrnb —enable-libopencore-amrwb —enable-libtheora —enable-libvorbis —enable-libvpx —enable-libx264 —enable-nonfree —enable-version3 —enable-static —disable-shared —extra-libs=-static —extra-cflags=-static' (length=323)
  
        3 => string '  libavutil      51. 64.100 / 51. 64.100' (length=40)
  
        4 => string '  libavcodec     54. 33.100 / 54. 33.100' (length=40)
  
        5 => string '  libavformat    54. 15.100 / 54. 15.100' (length=40)
  
        6 => string '  libavdevice    54.  1.100 / 54.  1.100' (length=40)
  
        7 => string '  libavfilter     3.  0.101 /  3.  0.101' (length=40)
  
        8 => string '  libswscale      2.  1.100 /  2.  1.100' (length=40)
  
        9 => string '  libswresample   0. 15.100 /  0. 15.100' (length=40)
  
        10 => string '  libpostproc    52.  0.100 / 52.  0.100' (length=40)
  
        11 => string 'Input #0, image2, from 'http://axiomchurch.co/main/wp-content/plugins/video-embed-thumbnail-generator/flash/skin/images/PlayNormal.png':' ; (length=136)
  
        12 => string '  Duration : 00:00:00.04, start : 0.000000, bitrate : N/A' (length=54)
  
        13 => string '    Stream #0:0 : Video : png, rgba, 100x100, 25 tbr, 25 tbn, 25 tbc' (length=66)
  
        14 => string '[graph 0 input from stream 0:0 @ 0x9482000] w:100 h:100 pixfmt:rgba tb:1/25 fr:25/1 sar:0/1 sws_param:flags=2' (length=109)
  
        15 => string '[output stream 0:0 @ 0x948ccc0] No opaque field provided' (length=56)
  
        16 => string '[auto-inserted scaler 0 @ 0x948d160] w:100 h:100 fmt:rgba sar:0/1 -> w:100 h:100 fmt:yuvj420p sar:0/1 flags:0x4' (length=111)
  
        17 => string '[mjpeg @ 0x948c760] ff_frame_thread_encoder_init failed' (length=55)
  
        18 => string 'Output #0, image2, to '/homepages/17/d411786663/htdocs/main/wp-content/uploads/2012/07/ffmpeg_exists_test%d.jpg' :' (length=113)
  
        19 => string '    Stream #0:0 : Video : mjpeg, yuvj420p, 100x100, q=2-31, 200 kb/s, 90k tbn, 25 tbc' (length=83)
  
        20 => string 'Stream mapping :' (length=15)
  
        21 => string '  Stream #0:0 -> #0:0 (png -> mjpeg)' (length=36)
  
        22 => string 'Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height' (length=119)
  

  The command being executed :

   /kunden/homepages/17/.../htdocs/bin/ffmpeg -i http://....co/main/wp-content/plugins/video-embed-thumbnail-generator/flash/skin/images/PlayNormal.png -ac 2 /homepages/17/.../htdocs/main/wp-content/uploads/2012/07/ffmpeg_exists_test.jpg

  You can see i have the full path of my ffmpeg binary and that it is executing. Here is what it looks like successfully via terminal :

      ffmpeg version git-2012-07-06-6936111 Copyright (c) 2000-2012 the FFmpeg developers
  
        built on Jul  5 2012 23:04:34 with gcc 4.4.3
  
        configuration : —prefix=' /ffmpeg' —enable-gpl —enable-libfaac —enable-libmp3lame —enable-libopencore-amrnb —enable-libopencore-amrwb —enable-libtheora —enable-libvorbis —enable-libvpx —enable-libx264 —enable-nonfree —enable-version3 —enable-static —disable-shared —extra-libs=-static —extra-cflags=-static
  
        libavutil      51. 64.100 / 51. 64.100
  
        libavcodec     54. 33.100 / 54. 33.100
  
        libavformat    54. 15.100 / 54. 15.100
  
        libavdevice    54.  1.100 / 54.  1.100
  
        libavfilter     3.  0.101 /  3.  0.101
  
        libswscale      2.  1.100 /  2.  1.100
  
        libswresample   0. 15.100 /  0. 15.100
  
        libpostproc    52.  0.100 / 52.  0.100
  
      Input #0, image2, from 'http://axiomchurch.co/main/wp-content/plugins/video-embed-thumbnail-generator/flash/skin/images/PlayNormal.png':
  
        Duration : 00:00:00.04, start : 0.000000, bitrate : N/A
  
          Stream #0:0 : Video : png, rgba, 100x100, 25 tbr, 25 tbn, 25 tbc
  
      [graph 0 input from stream 0:0 @ 0x9482000] w:100 h:100 pixfmt:rgba tb:1/25 fr:25/1 sar:0/1 sws_param:flags=2
  
      [output stream 0:0 @ 0x948ccc0] No opaque field provided
  
      [auto-inserted scaler 0 @ 0x948d160] w:100 h:100 fmt:rgba sar:0/1 -> w:100 h:100 fmt:yuvj420p sar:0/1 flags:0x4
  
      Output #0, image2, to '/homepages/17/d411786663/htdocs/main/wp-content/uploads/2012/07/ffmpeg_exists_test.jpg' :
  
        Metadata :
  
          encoder : Lavf54.15.100
  
          Stream #0:0 : Video : mjpeg, yuvj420p, 100x100, q=2-31, 200 kb/s, 90k tbn, 25 tbc
  
      Stream mapping :
  
        Stream #0:0 -> #0:0 (png -> mjpeg)
  
      Press [q] to stop, [?] for help
  
      frame=    1 fps=0.0 q=0.0 Lsize=       0kB time=00:00:00.04 bitrate=   0.0kbits/s    
  
      video:2kB audio:0kB subtitle:0 global headers:0kB muxing overhead -100.000000%
  

  The user running the script at terminal AND the apache user are the same user...i have verified this.

  Something about the environment apache is running through is killing me...i dont have access to apache error logs unfortunately.

  As a side note...i am trying to utilize the Video Embed & Thumbnail Generator for wordpress.

  Any help appreciated, thanks !